// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_WIN_MESSAGE_WINDOW_H_
#define BASE_WIN_MESSAGE_WINDOW_H_

#include <windows.h>

#include "base/base_export.h"
#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/strings/string16.h"
#include "base/threading/non_thread_safe.h"

namespace base {
namespace win {

    // Implements a message-only window.
    class BASE_EXPORT MessageWindow : public base::NonThreadSafe {
    public:
        // Used to register a process-wide message window class.
        class WindowClass;

        // Implement this callback to handle messages received by the message window.
        // If the callback returns |false|, the first four parameters are passed to
        // DefWindowProc(). Otherwise, |*result| is returned by the window procedure.
        typedef base::Callback<bool(UINT message,
            WPARAM wparam,
            LPARAM lparam,
            LRESULT* result)>
            MessageCallback;

        MessageWindow();
        ~MessageWindow();

        // Creates a message-only window. The incoming messages will be passed by
        // |message_callback|. |message_callback| must outlive |this|.
        bool Create(const MessageCallback& message_callback);

        // Same as Create() but assigns the name to the created window.
        bool CreateNamed(const MessageCallback& message_callback,
            const string16& window_name);

        HWND hwnd() const { return window_; }

        // Retrieves a handle of the first message-only window with matching
        // |window_name|.
        static HWND FindWindow(const string16& window_name);

    private:
        // Give |WindowClass| access to WindowProc().
        friend class WindowClass;

        // Contains the actual window creation code.
        bool DoCreate(const MessageCallback& message_callback,
            const wchar_t* window_name);

        // Invoked by the OS to process incoming window messages.
        static LRESULT CALLBACK WindowProc(HWND hwnd, UINT message, WPARAM wparam,
            LPARAM lparam);

        // Invoked to handle messages received by the window.
        MessageCallback message_callback_;

        // Handle of the input window.
        HWND window_;

        DISALLOW_COPY_AND_ASSIGN(MessageWindow);
    };

} // namespace win
} // namespace base

#endif // BASE_WIN_MESSAGE_WINDOW_H_
